a general understanding
Sub Sea Deviate Steerable Drill Bit
sub sea Steerable Motor Drill Bit
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Deviatory Drilling. Initially wells were drilled directly down. To dilineate the extent of the field or finding, the rig was moved to another location and another hole drilled directly down to establish contact with the reservoir. Since then things have developed. Improved means are available to indicate by seismic or other means what may be the extent of the field. Whilst drilling it became apparent that if one side of the drill bit became more loaded then an equalising reaction was generated moving the bit to slightly change direction. This action can be simulated by rotating a long knitting needle and putting a load on to one side, whereupon the needle will start to bow and the end move to the side. Based on these facts it became apparent that by drilling a hole in a location subsequent holes could be drillied in the same location and directed by deviation to progress out to etablish the exten of the reservoir or adjacent reservoirs withou moving the rig. To deviste the drill bit shows or slips were deigned ti induced the drill bit to drill offset and deviate. This can now be done without tripping (bringing the drill bit up to the surface) and to set the drill to deviate when required.
Steerable Drilling. A further development has been to motorise the drill bit at the drilling face using recirculated mud or other means to drive a turbine to rotate the drill bit. At the same time the direction can be changed by arching the articulated joints in the motor string to direct the bit. It is also now possible to measure / indicate the progress and direction of the drilling.
These changes mean that the approach to exploit a reservoir are a lot different from say 10 years ago. They have also encouraged the development of sub sea systems and modules. A satellite area can now be explored from one point and then linked up to a historical producing facility
Directional Drilling Jackover Embla